21515630 has 8 divisors (see below), whose sum is σ = 38728152. Its totient is φ = 8606248.

The previous prime is 21515629. The next prime is 21515633. The reversal of 21515630 is 3651512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21515596 and 21515605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515633) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1075772 + ... + 1075791.

It is an arithmetic number, because the mean of its divisors is an integer number (4841019).

Almost surely, 2^21515630 is an apocalyptic number.

21515630 is a deficient number, since it is larger than the sum of its proper divisors (17212522).

21515630 is a wasteful number, since it uses less digits than its factorization.

21515630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2151570.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 21515630 is about 4638.4943677879. The cubic root of 21515630 is about 278.1322542399.

The spelling of 21515630 in words is "twenty-one million, five hundred fifteen thousand, six hundred thirty".